System and method of optically inspecting manufactured devices
US6246788A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 6, 1998 |
| Grant date | Jun 12, 2001 |
| Priority date | — |
| Expiry date | May 6, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/014
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus, system, and method of optically inspecting printed circuit boards (PCBs) for defects, that reliably determines the dimensions of components including those having the same color as the background, and which can detect components which are missing, misoriented, misaligned, or not properly seated. The apparatus uses a camera and a coherent primary light source mounted at an angle away from the vertical so as to produce sharply defined PCB component shadows on the top surface of the PCB. An image of the PCB is captured, the shadow edges are symbolically decomposed into primitives from which gradients are produced, and then compared to a previously captured gradient of a defect-free PCB. Differences in the two image gradients, if any, are used to identify missing, misaligned, misoriented, and improperly seated components, and to detect foreign objects and other PCB defects.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.